This invention relates generally to gas turbine engines, and more particularly, to methods for replacing forged unitary combustor liners used with gas turbine engine combustors.
A turbine engine includes a compressor for compressing air which is mixed with a fuel and channeled to a combustor wherein the mixture is ignited within a combustion chamber for generating hot combustion gases. At least some known combustors include a dome assembly, a bolt banding, and liners to channel the combustion gases to a turbine. The turbine extracts energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator. The liners are coupled to the dome assembly at an upstream end with the bolt banding, and extend downstream from the bolt banding to define the combustion chamber.
At least some known liners are formed from forged and machined unitary bodies that include a plurality of cooling slots that are defined by integrally-formed overhanging portions. Accordingly, the regions of the liners adjacent such cooling slots are not subjected to the same degree of heat as other portions of the liner that are adjacent the combustion chamber, and as such, during operation thermal stresses may be induced within the liner. Over time, continued operation with thermal stresses may cause liners to thermally fatigue, causing weakening and/or cracking to develop within the liners.
Current repair methods include welding thermal fatigue cracks. Additionally, patches may be attached to areas of liners that are weakened by thermal stresses. However, if the thermal stresses have induced thermal fatigue or distress in larger areas of the liners, because of the complex shape of the liners, the combustor may not have enough structural integrity to enable patches to be attached. Furthermore, depending on the severity of the distress, welding patches within the liner may lead to a loss of dimensional stability of the liner. In such cases, repair of such liners is not a feasible option, and instead the entire combustor liner is replaced. Because the liner is coupled to the bolt band and the dome assembly, often the entire combustor must be disassembled for the liner to be replaced. Furthermore, when the fasteners are removed from the bolt band and dome assembly, precise dimensional relations between the components may be altered and as a result, special tooling may be required during re-assembly. Thus, replacing a forged combustor liner including cooling slots may be a time-consuming and expensive process.